Generating laser pulses based on chirped pulse amplification

Abstract

Techniques and devices for producing short laser pulses based on chirped pulse amplification.

What is claimed is: 
     
       1. A method for amplifying laser pulses, comprising:
 operating an input optical amplifier to amplify input laser pulses to produce laser pulses that have a linear chirp in frequency and are stretched to have a pulse duration longer than a pulse duration of each input laser pulse; 
 operating an optical pulse stretcher down stream from the initial optical amplifier to further stretch durations of the laser pulses to produce stretched laser pulses that have a reduced peak power in each laser pulse; 
 directing the stretched laser pulses into an optical amplifier to amplify the stretched laser pulses to produce amplified stretched laser pulses; 
 compressing a pulse duration of each of amplified stretched laser pulses to produce amplified and compressed output laser pulses with a high peak power; 
 operating an optical pre-amplifier located between the optical pulse stretcher and the optical amplifier to amplify each stretched laser pulse output by the optical pulse stretcher prior to amplification by the optical amplifier; 
 before directing laser pulses output by the pre optical amplifier into the optical amplifier, reducing a pulse repetition rate of the laser pulses; and 
 maintaining the reduced pulse repetition rate higher than a threshold pulse repetition rate to reduce an instability in the optical amplifier or to reduce amplified spontaneous emission in the optical amplifier. 
 
     
     
       2. The method as in  claim 1 , comprising:
 further reducing the reduced pulse repetition rate of the amplified stretched laser pulses, prior to compressing the laser pulses, to a desired output pulse repetition rate; and 
 subsequently, performing the compressing of the duration of each pulse to produce the amplified and compressed output laser pulses at the desired output pulse repetition rate. 
 
     
     
       3. The method as in  claim 1 , comprising:
 filtering an optical spectrum of the laser pulses at a location downstream from the optical pulse stretcher and upstream from the optical amplifier to reduce a distortion in the laser pulses. 
 
     
     
       4. The method as in  claim 1 , comprising:
 before directing laser pulses into the optical amplifier, reducing a pulse repetition rate of the laser pulses. 
 
     
     
       5. The method as in  claim 4 , comprising:
 maintaining the reduced pulse repetition rate higher than a threshold pulse repetition rate to reduce an instability in the optical amplifier or to reduce amplified spontaneous emission in the optical amplifier. 
 
     
     
       6. The method as in  claim 1 , comprising:
 further reducing the reduced pulse repetition rate of the amplified stretched laser pulses, prior to compressing the laser pulses, to a desired output pulse repetition rate; and 
 subsequently, performing the compressing of the duration of each pulse to produce the amplified and compressed output laser pulses at the desired output pulse repetition rate. 
 
     
     
       7. The method as in  claim 1 , comprising:
 filtering an optical spectrum of the laser pulses at a location downstream from the optical pulse stretcher and upstream from the optical amplifier to reduce a distortion in the laser pulses. 
 
     
     
       8. The method as in  claim 1 , comprising:
 controlling the input laser pulses at a location prior to the initial optical amplifier to have spectral distortions less than 10 dB. 
 
     
     
       9. The method as in  claim 1 , comprising:
 operating the optical pulse stretcher to stretch a duration of each pulse by a factor of 10 or more to produce the stretched laser pulses. 
 
     
     
       10. The method as in  claim 1 , wherein:
 the amplified and compressed output laser pulses have a pulse energy greater than 10 micro joules. 
 
     
     
       11. The method as in  claim 1 , wherein:
 the amplified and compressed output laser pulses have a pulse duration less than 10 picoseconds. 
 
     
     
       12. The method as in  claim 1 , comprising:
 keeping a fiber length of a fiber amplifier as the optical amplifier to be sufficiently short to reduce nonlinear distortions in the optical amplifier. 
 
     
     
       13. The method as in  claim 1 , wherein:
 configuring the optical amplifier to have an optical gain greater than 35 dB. 
 
     
     
       14. The method as in  claim 1 , wherein:
 the initial optical amplifier is a parabolic optical amplifier, and the laser pulses output by the initial optical amplifier have a parabolic pulse shape in time. 
 
     
     
       15. A pulsed laser device, comprising:
 a pulsed seed laser that produces input laser pulses; 
 an initial optical amplifier that receives the input laser pulses to amplify the received input laser pulses to produce laser pulses that have a linear chirp in frequency and a pulse duration longer than a pulse duration of each input laser pulse; 
 an optical pulse stretcher located down stream from the initial optical amplifier to further stretch durations of the laser pulses to produce stretched laser pulses that have a reduced peak power; 
 an optical amplifier to further amplify the stretched laser pulses to produce amplified stretched laser pulses; 
 a pulse compressor that compresses a pulse duration of each pulse in the amplified stretched laser pulses to produce amplified and compressed output laser pulses with a high peak power; and 
 a pulse picking device located upstream from the optical amplifier to reduce a pulse repetition rate of the stretched optical pulses, wherein the pulse picking device controls the reduced pulse repetition rate of the stretched optical pulses to be greater than a threshold pulse repetition rate above which an instability or amplified spontaneous emission in the optical amplifier is reduced. 
 
     
     
       16. The device as in  claim 15 , wherein:
 the pulse stretcher includes a chirped fiber Bragg gating that stretches the laser pulses. 
 
     
     
       17. The device as in  claim 16 , wherein:
 the chirped fiber Bragg grating is structured to, in addition to stretching the laser pulses, perform optical filtering of an optical spectrum of the laser pulses to reduce a distortion in the stretched laser pulses. 
 
     
     
       18. The device as in  claim 17 , wherein:
 the chirped fiber Bragg grating is structured to remove spectral components near an edge of a spectral shape of the laser pulses. 
 
     
     
       19. The device as in  claim 15 , comprising:
 an optical bandpass filter located in an optical path of the laser pulses between the initial optical amplifier and the optical amplifier to filter an optical spectrum of the laser pulses to reduce a distortion in the laser pulses prior to entering the optical amplifier. 
 
     
     
       20. The device as in  claim 15 , comprising:
 a second pulse picking device located between the optical amplifier and the pulse compressor to further reduce the pulse repetition rate of the amplified stretched laser pulses to a desired output pulse repetition rate. 
 
     
     
       21. The device as in  claim 20 , wherein:
 the second pulse picking device includes an acousto-optic modulator that receives input light to produce a diffraction beam along a direction different from a direction of the input light, and a prism located to receive the diffraction beam to produce output light. 
 
     
     
       22. The device as in  claim 15 , wherein:
 the optical amplifier includes a fiber gain section doped to produce an optical gain for the laser pulses under optical excitation of optical pump light at a pump wavelength different from a laser wavelength of the laser pulses, a coupler that couples pump light into the fiber gain section in a propagation direction of the laser pulses in the fiber gain section, a collimator lens that couples light out of the fiber gain section, and a pump dump coupled to one side of the fiber gain section that is close to the collimator lens to separate the pump light from the light of the laser pulses. 
 
     
     
       23. The device as in  claim 15 , wherein:
 the optical amplifier includes a fiber gain section doped to produce an optical gain for the laser pulses under optical excitation of optical pump light at a pump wavelength different from a laser wavelength of the laser pulses, a coupler that couples pump light into the fiber gain section in a propagation direction of the laser pulses in the fiber gain section, a collimator lens that couples light out of the fiber gain section, and a dichroic reflector that separates pump light and light of the laser pulses. 
 
     
     
       24. The device as in  claim 15 , wherein:
 the optical amplifier includes a fiber gain section doped to produce an optical gain for the laser pulses under optical excitation of optical pump light at a pump wavelength different from a laser wavelength of the laser pulses, a coupler that couples pump light into the fiber gain section in a direction opposite to a propagation direction of the laser pulses in the fiber gain section, a pump dump coupler coupled to the fiber gain section at an opposite side of the coupler to couple residual pump light out of the fiber gain section, a collimator lens that couples light of laser pulses out of the fiber gain section and collimates the light toward the pulse compressor. 
 
     
     
       25. The device as in  claim 15 , wherein:
 the optical amplifier includes a fiber gain section doped to produce an optical gain for the laser pulses under optical excitation of optical pump light at a pump wavelength different from a laser wavelength of the laser pulses, a pump light source that produces the optical pump light, a dichroic reflector that receives the optical pump light from the pump light source and reflects the optical pump light towards the fiber gain section, a collimator lens that couples the reflected optical pump light from the dichroic reflector into the fiber gain section in a direction opposite to a propagation direction of the laser pulses in the fiber gain section, and a pump dump coupler coupled to the fiber gain section at an opposite side of the collimator lens to couple residual pump light out of the fiber gain section, wherein the laser pulses amplified by the fiber gain section transmit through the dichroic reflector towards the pulse compressor. 
 
     
     
       26. The device as in  claim 15 , comprising:
 a pre optical amplifier located between the optical pulse stretcher and the optical amplifier. 
 
     
     
       27. A pulsed laser device, comprising:
 a pulsed seed laser that produces input laser pulses; 
 an optical pulse stretcher located down stream from the seed laser to stretch durations of the laser pulses originated from the input laser pulses to produce stretched laser pulses that have a reduced peak power; 
 an optical amplifier located down stream from the optical pulse stretcher to receive the stretched laser pulses and to amplify the stretched laser pulses to produce amplified stretched laser pulses; 
 a pulse compressor that is located down stream from the optical amplifier and compresses a pulse duration of each received laser pulse to produce a compressed laser pulse with a high peak power; and 
 a pulse picking device located between the optical pulse stretcher and the pulse compressor and to reduce a pulse repetition rate of received laser pulses, the pulse picking device including an acousto-optic modulator that receives input light to produce a diffraction beam along a direction different from a direction of the input light, and a prism located to receive the diffraction beam to produce output light by correcting an angular beam distortion and by reducing an optical loss in the produced output light output by the prism. 
 
     
     
       28. The device as in  claim 27 , wherein:
 the pulse picking device is located between the optical amplifier and the pulse compressor. 
 
     
     
       29. The device as in  claim 27 , wherein:
 the pulse picking device is located between the optical pulse stretcher and the optical amplifier. 
 
     
     
       30. The device as in  claim 27 , comprising:
 a second optical amplifier located between the optical amplifier and the pulse compressor to provide additional amplification of each laser pulse. 
 
     
     
       31. The device as in  claim 30 , wherein:
 the pulse picking device is located between the optical amplifier and the second optical amplifier. 
 
     
     
       32. The device as in  claim 27 , comprising:
 an optical parabolic amplifier between the seed laser and the optical pulse stretcher, the optical parabolic amplifier amplifying the input laser pulses to produce parabolic laser pulses that have a parabolic pulse and spectral shape and are stretched to have a pulse duration longer than a pulse duration of each input laser pulse; and 
 an optical bandpass filter located in an optical path of the laser pulses between the parabolic optical amplifier and the optical amplifier to filter an optical spectrum of the laser pulses and to remove spectral components near an edge of a parabolic spectral shape of the laser pulses to reduce a distortion in each amplified stretched laser pulse output by the optical amplifier. 
 
     
     
       33. The device as in  claim 27 , wherein the pulse picking device controls the reduced pulse repetition rate of the stretched optical pulses to be greater than a threshold pulse repetition rate above which an instability or amplified spontaneous emission in the optical amplifier is reduced.